Langflow DB Repair

Langflow Database Repair

This skill handles the common "Database Mismatch" crash in Langflow caused by schema/model divergence (often involving column comments).

Common Symptoms

• Langflow process starts but immediately exits.
• langflow.log contains: RuntimeError: There's a mismatch between the models and the database.
• langflow migration --fix fails with alembic.script.revision.RevisionError: Ambiguous walk.

Workflows

1. Automated Repair

The skill includes a bundled script that automates the safety backup, the standard fix, and the manual "Julia-method" sync if needed.

bash scripts/repair_langflow_db.sh

2. Manual Diagnostics

If the script is not used, follow these steps:

1. Check Alembic Heads: Identify if multiple heads exist.

   cd /mnt/data/system/services/langflow && source venv/bin/activate
   cd venv/lib/python3.12/site-packages/langflow && alembic -c alembic.ini heads
   

2. Verify DB Version:

   psql -h localhost -U postgres -d langflow -c "SELECT * FROM alembic_version;"
   

3. Manual Sync (The Julia Method): If comments are the only diff, apply them manually:

   COMMENT ON COLUMN flow.name IS 'Name of the flow (e.g., RAG Bot).';
   COMMENT ON COLUMN flow.description IS 'User-provided summary of the flow.';
   COMMENT ON COLUMN flow.data IS 'Visual node-and-edge graph data.';
   COMMENT ON COLUMN flow.id IS 'Unique identifier for the flow.';
   

Resources

• scripts/repair_langflow_db.sh: The primary automation script.